RU2723395C1 - Scintillation material and method for its production - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to scintillation inorganic oxide monocrystals with garnet structure containing gadolinium, yttrium, cerium, beryllium and solted by at least one element of the second group of Mg, Ca, Sr. Technical result is achieved due to fact that containing yttrium and gadolinium monocrystal with garnet structure is doped with cerium and beryllium and one of elements of second group of Ba, or Sr, or Ca at specified ratio. This monocrystal is produced by Czochralski method with subsequent isothermal annealing.EFFECT: invention increases output of scintillations, reduces its temperature dependence, shortens scintillation kinetics and increases energy resolution of scintillation detectors when detecting ionizing radiation.10 cl, 2 tbl

Description

The invention relates to scintillation materials with a garnet structure, in particular to inorganic single crystals activated by ions of the rare-earth element cerium Ce, in which light flashes of scintillations occur under the action of ionizing radiation, and are intended for sensors of ionizing studies in medical diagnostics, environmental monitoring, non-destructive testing and mineral exploration, experimental physics, space measuring devices. The invention also relates to a technology for producing scintillation single crystals with a garnet structure containing gadolinium and yttrium ions doped with Ce and Be ions, co-alloyed with one of the elements of the second group Mg, Ca, Sr to modify the scintillation properties of the single crystal.

Phosphors are used to convert various types of energy into light. Scintillators are phosphors in which short-term flashes of light - scintillations (flashes of luminescence) occur under the influence of ionizing radiation. The atoms or molecules of the scintillator due to the energy of charged particles go into an excited state, and the subsequent transition from an excited to a normal state is accompanied by the emission of luminescence, also called scintillation. The scintillation mechanism, its emission spectrum, and the duration of emission depend on the nature of the luminescence centers and the material where they are embedded.

The emitted number of photons is proportional to the absorbed energy of ionizing radiation, which allows one to obtain the energy spectra of this radiation. In a scintillation detector, the light emitted during scintillation is collected at a photodetector, converted into an electrical signal, which is amplified and recorded by one or another recording system. The emission spectrum of scintillation material should be optimally matched with the spectral sensitivity of the photodetector used. The emission spectrum of the scintillation material inconsistent with the spectral sensitivity of the receiver impairs the energy resolution of the scintillation detector.

The scintillator glow can be due to both the properties of the base material and the presence of an impurity, an activator. Scintillators that glow without an activator are called self-activated. To increase the light output, i.e. the number of photons emitted by the scintillator during the absorption of a certain amount of energy, the so-called activator is introduced into the crystal. The activator forms glow centers in the main substance (base).

Crystal scintillators characterize the following properties: wavelength (λ _max ), which corresponds to the maximum of the luminescence spectrum; scintillator transparency range in the wavelength region (λ _max ); flashing kinetics time constant (τ); light output, which are determined at a given (working) temperature. The ability to detect ionizing radiation characterize the density of the basic substance; effective atomic number (Z _eff. ); refractive index.

A scintillation detector is a device for recording ionizing radiation and elementary particles (protons, neutrons, electrons, γ-quanta, etc.), the main elements of which are material that is luminescent under the influence of charged particles (scintillator) and a photodetector. Detection of neutral particles (neutrons, γ-quanta) occurs by secondary charged particles formed by the interaction of neutrons and γ-quanta with scintillator atoms.

For spectrometry of γ-quanta and charged particles in a wide energy range, materials are used that have a high density and a high effective atomic number. The detection efficiency of gamma rays is determined by the density of matter and the effective atomic number Z _eff. The kinetics of scintillation determines the load capacity of the detector and the time of data acquisition for a given statistic. The output of scintillations determines the energy resolution during registration of neutral particles: γ-quanta and neutrons; as well as charged particles: electrons, positrons, protons and ionized nuclei. Together, the registration efficiency, energy resolution, and kinetics of scintillations determine the applicability and scope of the scintillation material for recording ionizing radiation.

Cross-luminescence scintillators are known that have the shortest scintillation emission time (see P. Lecoq, et.al., Inorganic Scintillators for Detector Systems, 2017, Springer, P. 408). The decay time constant of the fast scintillation component is 600 picoseconds, but its output does not exceed 2000 photons per 1 MeV of absorbed γ-ray energy, which makes the detector based on it unsuitable for γ-ray spectrometry and use in the medical diagnostics and non-destructive testing devices using the spectrum X-ray and γ-ray sources in the energy range up to 1 MeV.

Self-activated scintillation single crystals of CeBr ₃ , Bi ₄ Ge ₃ O ₁₂ , CdWO ₄ , PbWO _{4 are} known, which have high detection efficiency of ionizing radiation, however, Bi ₄ Ge ₃ O ₁₂ , CdWO ₄ crystals have slowly decaying scintillations, and PbWO ₄ crystals have low scintillation output (US patent, 7279120; RU patent, 2031987, and RU patent, 2132417). To increase the light output, a self-activated scintillation crystal is cooled, which works well in crystals of this type, the structural units of which (oxy-anion complexes) have significantly temperature-quenched luminescence. In PbWO ₄ crystals, cooling to a temperature of minus 25 ° С allows you to triple its light output while maintaining a short luminescence time, but this does not provide an acceptable energy resolution when registering γ-rays in the energy range of less than 1 MeV, which makes them unsuitable for use in devices medical diagnosis. With increasing temperature, additional temperature quenching of scintillations occurs; in the temperature range from 20-150 ° С, the output of scintillations in Bi ₄ Ge ₃ O ₁₂ decreases with a coefficient of -1.2% / degree, which leads to almost complete quenching of scintillations at 100 ° С. CeBr ₃ crystals (US patent 7405404) have a high scintillation yield and short scintillation emission kinetics, however, the crystals are highly hygroscopic, difficult to manufacture, and unsuitable for the manufacture of detector arrays consisting of many scintillation elements and used in medical diagnostics.

A widely used type of scintillation materials are activated scintillators. A variety of scintillator parameters can be obtained by varying activators and base composition (see P. Lecoq, et.al., Inorganic Scintillators for Detector Systems, 2017, Springer, p. 408, International Patent Application PCT / EP2001 / 001838; international publication WO / 2001 / 060945). The most common activator for creating scintillation materials with a high yield and fast decay kinetics is the Ce ion in the trivalent state. In contrast to self-activated scintillation crystals, the luminescence of a scintillation single crystal doped with cerium ions is due to inter-configuration d-f luminescence, which has a high quantum yield and a slight quenching effect near room temperature. Known scintillation single crystals activated by cerium Ce ions (the content of the activator in the crystalline matrix is from tenths of a percent to units of percent), which have one of the largest scintillation yields (see, for example, US patent 10197685, US patent 8278624 U.S. Patent 7,250,609; U.S. Patent 7479637). Among the scintillation crystals activated by cerium ions, there are materials with a garnet structure having a cubic space symmetry group. These crystals are the most technologically advanced; they allow one to obtain a wide range of compositions for use in scintillation detectors.

Unlike self-activated scintillators, in cerium-based scintillators of activated crystals, the temperature dependence of the scintillation yield is determined by the energy gap between the bottom of the conduction band and the radiative state of cerium ions. With increasing temperature, thermal ionization of electrons from the excited state of the activator to the conduction band occurs, which leads to a decrease in the yield of scintillations and, as a consequence, to a decrease in the energy resolution. With decreasing temperature, small electron and hole traps formed in crystals based on point defects provide additional slow components in scintillation, as well as phosphorescence, which leads to an increase in the level of afterglow in the crystal, redistribution of the emitted light in favor of phosphorescence, and a decrease in the yield of scintillations and, as a result, a deterioration in energy resolution.

Known scintillation material in the form of yttrium aluminum garnet Y ₃ Al ₅ O ₁₂ activated by cerium ions Ce ³⁺ for registration of γ-quanta. In a single crystalline form, the material has a maximum density of 4.55 g / cm ³ and an effective charge Z _eff. = 32, which ensures efficient registration of low-energy γ-quanta and electrons, the crystal has a small temperature dependence of the scintillation yield

(https://www.crystals.saint-gobain.com/sites/imdf.crystals.com/files/documents/yag-material-data-sheet_69775.pdf): in the temperature range 25-150 ° С the temperature coefficient of change of the output scintillation is - 0.24% / degree, however, the material remains ineffective for use for recording γ-quanta with energies of more than 500 keV, used, for example, in positron emission tomographs and applications that use measurement in exploration wells at elevated temperatures. The scintillation yield of such a material does not exceed 30000 ph / MeV, which in combination with a small effective charge Z _eff. makes it unsuitable for spectrometric measurements of gamma rays with energies of more than 500 keV.

JP Patent Document 20130433960 discloses a scintillation crystal of a Lu ₃ Al ₅ O ₁₂ alumina-lutetium garnet for detecting gamma rays. In a single-crystalline form, the crystal has a maximum density of 6.7 g / cm ³ and an effective charge Z _eff = 63, which ensures efficient registration of γ-quanta in a wide energy range. When activated by praseodymium (Yanagida et. Al., Jpn. J. Appl. Phys. (2013) 52, 07640), the yield of scintillations has a complex temperature dependence: with an increase in temperature from 20 to 80 ° C, it increases with a coefficient of plus 0.3% / degree , and in the range of 80-150 ° C decreases with a coefficient of minus 0.7% / degree. As a result, a decrease in the yield of scintillations in the indicated temperature range is not more than 30% with respect to room temperature. However, the scintillation yield of such a material does not exceed 16,000 photons / MeV, which makes it unsuitable for spectrometric measurements of γ-quanta with energies of more than 500 keV and in a wide temperature range.

The shortening of the kinetics of scintillation in inorganic materials with a yttrium-based garnet structure is achieved in mixed garnets (based on yttrium ions, aluminum and gallium ions) when the compound is activated by cerium ions (O.Sidletskiy et al., Enginering of bulk and fiber-shaped YAGG: Ce scintillator crystals, CrysEngCom (2017) 6, 1001-1007). The scintillation single crystal Y ₃ Ga ₃ Al ₂ O ₁₂ , activated by cerium ions or co-ionized, has fast scintillation kinetics and can be used to detect gamma rays. However, the partial replacement of aluminum ions by gallium ions does not lead to a significant increase in the density and Z _eff , which makes it unsuitable for spectrometric measurements of γ quanta with energies of more than 500 keV and in a wide temperature range.

The complex composition and structure of the known scintillation crystal, including yttrium, gallium and aluminum ions, for example, Y ₃ Ga ₃ Al ₂ O ₁₂ , as well as the tendency of one of the main components, gallium, to escape from the melt, cause an increased concentration of defects, in particular, oxygen vacancies (see Lamoreaux R N., et all. "High Temperature Vaporization Behavior of Oxides II. Oxides of Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb , Zn, Cd, and Hg "J. Phys. Chem. Ref. 1987, data 16 419-43). Oxygen vacancies are electron capture centers, which leads to phosphorescence in scintillation material due to electron tunneling to luminescence centers - trivalent cerium ions Ce ³⁺ . In order to eliminate the capture of nonequilibrium electrons by oxygen vacancies, ions of the second group, Mg, Ca, Sr, non-isovalently replacing yttrium Y ions are introduced into the crystal in addition to the crystal growth mixture. Mg, Ca, Sr ions replace yttrium ions in the matrix. With the indicated non-isovalent substitution, a deep electron capture center is formed in the garnet crystalline matrix, which ensures fast capture of the trapped carriers from lower levels, thereby preventing interaction due to tunneling of carriers from small traps to cerium ions Ce ³⁺ and gadolinium Gd ³⁺ . Trapped in a deep level, an electron recombines through a non-radiative channel. Non-isovalent doping provides a decrease in phosphorescence.

An increase in the yield of scintillations in inorganic materials with a garnet structure is achieved by replacing yttrium or lutetium ions in the raw materials for growing crystals with gadolinium ions (see, for example, US patent 9193903 and JP patent 2014094996), and aluminum ions with a pair of ions: aluminum and gallium upon activation of the compound by cerium ions. Such compounds were obtained in the form of polycrystalline transparent ceramics (Cherepy NJ, Seeley ZM, Payne SA, Beck PR, Drury OB, O'Neal SP, Morales Figueroa K, Hunter S, Ahle L, Thelin PA, Stefanik T, Kindem J (2013) Development of Transparent Ceramic Ce-Doped Gadolinium Garnet Gamma Spectrometers. IEEE Trans Nucl Sci 60: 2330-2335). Ceramics of yttrium-gadolinium-aluminum-gallium garnet with the structural formula (Y-Gd) ₃ Al ₂ Ga ₃ O ₁₂ , activated by cerium ions, has a high scintillation yield, a density of 5.8 g / cm ³ , effective charge Z _eff = 45 and provide high energy resolution during registration of γ-quanta. A disadvantage of the known scintillation ceramics is the presence of slow components in the kinetics of scintillation, which does not allow it to be used at high loads when detecting γ quanta.

The fraction of slow components in the kinetics of scintillations and the phosphorescence of scintillation material activated by cerium ions significantly decrease upon co-activation of the scintillation material by divalent ions Mg, Ca, Sr. Gd ₃ Al ₂ Ga ₃ O ₁₂ scintillation single crystal materials are known, activated by cerium ions and co-activated by magnesium ions of Mg with a low concentration of about 10 ppm, (G. Tamulaitis et al., Improvement of the time resoltion of radiation detectors based on Gd ₃ Al ₂ Ga ₃ O ₁₂ scintillators with SiPM readout, IEEE Trans. Nucl. Sci. (2019) 66, issue 7), obtained by the Czochralski method. Co-doping impurities are introduced into the melt and, with a small gradient along the growth axis, are distributed in the crystal. In such crystals, slow components and phosphorescence are substantially suppressed. However, additional co-activation by non-isovalent Mg ions with a uniform volume distribution is difficult to achieve during ceramic production, especially with small amounts of Mg co-activator. The introduction of co-doping impurities in significant quantities leads to a decrease in the yield of scintillations, which is due to a decrease in the content of cerium ions in the trivalent state of Ce ³⁺ . Thus, with an increase in the content of magnesium ions to 0.4%, the yield of scintillations in the Gd ₃ Al ₂ Ga ₃ O ₁₂ single crystal decreases by a factor of 2. Thus, a disadvantage of the known scintillation material Gd ₃ Al ₂ Ga ₃ O ₁₂ , activated by cerium ions Ce ³⁺ and coactivated Mg, is the reduced yield of scintillations with respect to the scintillation material Gd ₃ Al ₂ Ga ₃ O ₁₂ , activated by cerium ions.

Monocrystalline scintillation material with a garnet structure activated by cerium ions and co-activated by magnesium and titanium ions and described by the chemical formula ((Gd _1-r Y _r ) _1-sx Me _s Ce _x ) _3-z (Ga _1-yq Al _y Ti _q ) _{5 + z} O ₁₂ . Combined activation allows achieving improved operational parameters, scintillation yield, amplitude resolution, and time resolution at lower temperatures in the temperature range from -45 ° C to + 20 ° C, which can significantly improve the operational parameters of the detectors by reducing the noise of semiconductor photodetectors (M .Korjik et al., Significant improvement of GAGG: Ce based scintillation detector performance with temperature decrease, NIM A 871 (2017) 42-46; G. Tamulaitis et.al., Improvement of the Time Resolution of Radiation Detectors Based on Gd ₃ Al ₂ Ga ₃ O ₁₂ Scintillators With SiPM Readout, IEEE Trans. Nucl. Sci. 66 (2019) 1879-1888]. However, when the temperature rises above 50 ° C, the yield of scintillations of such a crystal undergoes a significant decrease, and upon reaching temperature of 150 ° C is practically zero.

Currently, there are no scintillation materials that would possess the optimal set of parameters for solving the problems mentioned above. In the prior art, there is a need for scintillation materials combining a high scintillation yield over a wide temperature range from plus 25 ° C to plus 150 ° C, inclusive, as well as high detection efficiency of ionizing radiation and short scintillation emission times with a minimum level of slow components and afterglow of the material . Such a need is caused, for example, by the operating conditions of the material in wells designed for hydrocarbon exploration, where, depending on the measurement method, the detection of both the natural radioactivity of the rock around the well depending on the depth and γ-quanta induced in the rock by neutron sources is used. High scintillation yield in combination with fast kinetics provide high temporal and energy resolution of the scintillation detector in a wide range of both energies and temperatures.

The scintillation properties of materials substantially depend on the methods for their preparation. The luminescent and scintillation properties of materials obtained by various methods are far from identical. The observed differences in the optical properties of crystals are primarily associated with differences in the main types and concentrations of defects in the structure of garnets, which are different types of vacancies in garnet single crystals, including oxygen, as well as the redistribution of the main components in the structure of garnet due to the dissociative evaporation of its highly volatile components with high saturated vapor pressure, for example, various suboxides of gallium Ga ³⁺ or aluminum Al ³⁺ . The formation of such defects is an inevitable consequence of the high growth temperature of bulk crystals of garnets from the melt (temperature of about 1700 ° C -2000 ° C). The concentration of such defects in garnet crystals doped with rare-earth ions is comparable with the concentration of activator ions. When using gaseous media with different oxygen partial pressures for crystal growth, significant differences are also observed in the concentration of vacancy defects, primarily oxygen vacancies.

In mixed garnets, additional defect formation is observed due to a disordered structure due to the random distribution of matrix-forming ions in the crystal lattice. The disordering of the structure leads to significant random modulation of the bottom of the conduction band and, as a result, to the formation of a multiplicity of small traps of nonequilibrium carriers formed in the scintillator during interaction with ionizing radiation. This leads to an increase in the fraction of slow components in the scintillation pulse. The disorder cannot be eliminated in mixed crystals due to the random distribution of ions of the same type in the crystal, but its effect can be minimized by using additional doping additives to cerium.

Within the framework of this application, the complex task of obtaining a single crystal with a garnet structure for scintillation sensors with a sufficient density and effective charge Z _eff , which would allow to obtain in the extended temperature range from plus 25 ° С to plus 150 ° С, inclusive, the highest yield of scintillations with simultaneous shortening the duration of the main component of the kinetics of scintillations and the minimum level of afterglow for detecting gamma rays in a wide energy range. The problem of obtaining a single crystal with a garnet structure that is suitable for spectrometric measurements of gamma rays in a wide energy range and temperature range from plus 25 ° C to plus 150 ° C, inclusive, is also being solved.

In addition, the task of developing a technology for producing such oxide single crystals with a garnet structure is solved to modify their scintillation and optical properties by doping with cerium and beryllium ions and segregating with elements of the second group Mg, Ca, Sr.

The problem is solved in that a scintillation material with a garnet structure for scintillation sensors is a compound described by the chemical formula ((Gd _1-r Y _r ) _1-sx Me _s Ce _x ) _3-z (Ga _1-yq Al _y Be _q ) _{5 + z} O ₁₂ , where the q value is in the range from 0.00001 to 0.02; the value of r is in the range from 0.05 to 0.95; the value of x is in the range from 0.001 to 0.01; the value of y is in the range from 0.2 to 0.6; the value of z is in the range from -0.2 to 0.2; the value of s is in the range from 0.0001 to 0.1, while Me denotes at least one element from the series Mg, Ca, Sr.

It is preferable that upon irradiation with gamma rays of the aforementioned compound, the fluorescent component generates radiation at a wavelength in the range of 480-680 nm, and the light output at a temperature of 25 ° C is not less than 51,000 ph / MeV.

In addition, it is preferable that the light output when irradiated with a Cs-137 gamma source with an energy of 662 keV gamma rays at a temperature of + 150 ° C is at least 20,000 phot / MeV, while the light output when irradiated with a Cs-137 gamma source the energy of gamma rays of 662 keV at a temperature in the temperature range of 25-150 ° C varies with a speed of no more than -0.4% / degree, and the duration of the main component of the kinetics of scintillation is not more than 55 ns.

It is also advisable that the proportion of the main component of the kinetics of scintillation is at least 85%; and the phosphorescence level after 100 s is no more than 0.5%.

The problem is also solved by the fact that the method of obtaining scintillation material with a garnet structure for scintillation sensors, which is a compound described by the chemical formula ((Gd _1-r Y _r ) _1-sx Me _s Ce _x ) _3-z (Ga _1-yq Al _y Be _q ) _{5 + z} O ₁₂ , includes the preliminary preparation of a mixture of stoichiometric composition in accordance with the chemical formula from a mixture of oxides Gd, Y, Ga, Al, Mg, Be, as well as the introduction of cerium in the form of a compound taken from the series oxide or fluoride or chloride, as well as Ba or Sr or Ca in the form of carbonate, and the subsequent growth of single crystals from the resulting mixture according to the Czochralski method.

Preferably, the growth of single crystals by the Czochralski method is carried out in a protective atmosphere based on argon or nitrogen with the addition of oxygen in a concentration from the range from 0.0001 to 5 vol. %

In addition, the grown single crystal is subjected to isothermal annealing at a temperature from the range of 500–950 ° C for a time from the range of not more than 100 hours, either in air or in an inert gas atmosphere or in vacuum.

The invention is illustrated by non-limiting examples of its implementation, as well as tables 1 and 2. Table 1 shows the main parameters of known scintillation materials.

Table 2 shows the compositions and characteristics of experimental samples of scintillation crystals in accordance with this application.

These single crystals with a pomegranate structure of the claimed chemical formula and containing a group of dopant and salt-containing impurities to modify its scintillation and optical properties were obtained by growing from a melt according to the Czochralski method, according to the claimed method. This method includes loading into a crucible a pre-synthesized charge, the composition of which corresponds to the composition of the compound described by the formula ((Gd _1-r Y _r ) _1-sx Me _s Ce _x ) _3-z (Ga _1-yq Al _y Be _q ) _{5+ z} O ₁₂ , and q is in the range from 0.00001 to 0.02; r is in the range from 0.05 to 0.95; x is in the range from 0.001 to 0.01; y is in the range from 0.2 to 0.6; z is in the range from -0.2 to 0.2; s is in the range from 0.0001 to 0.1, with Me denoting at least one element from the series Mg, Ca, Sr, creating a protective atmosphere, subsequent melting of the charge, introducing a rotating seed oriented crystal into contact with the surface of the melt drawing an oriented crystal from a melt. As a seed oriented crystal, a pomegranate crystal is used that most closely matches the composition of the grown crystal.

To prepare the initial mixture using the original components in the form of oxides or carbonates with an initial purity of not worse than 99.99%. The impurity content in these starting components should be minimal and not exceed 1 ppm for any of the impurity elements. The pre-dried starting oxides or carbonates are weighed in accordance with the chemical formula of the synthesized crystal, thoroughly mixed and the mixture is synthesized at a temperature of at least 1400 ° C for at least 8 hours.

The resulting mixture is loaded into an iridium crucible and placed in the growth chamber of the apparatus for growing single crystals.

Thermal insulating ceramics are placed around the crucible in such a way as to ensure thermal insulation of the crucible and optimal temperature conditions for the growth and preservation of the grown single crystal. Also, a seed holder with a pre-oriented seed crystal of gadolinium-aluminum-gallium garnet is fixed to the upper working rod of the growing installation. Then the installation is closed and vacuum, followed by the inlet of a protective atmosphere based on argon or nitrogen with a slight addition of oxygen in a concentration of from 0.0001 to 5 vol. % After that, heating is carried out at a given speed until the initial charge is melted, the melt is homogenized by holding it for a certain time from 1 minute to several hours, followed by seeding. Seeding is the process of contact of a seed crystal with the surface of the melt. The seed crystal in this case rotates with a frequency from the range of 5-30 min ^-1 . After seeding, the upper working rod begins to move upward at a certain speed from the range of 0.1-5 mm / hour. Subsequently, in accordance with a predetermined growing program, a single crystal is formed, which, upon reaching a certain weight, is separated from the melt either due to the accelerated movement of the upper working rod or due to additional heating of the melt. The grown single crystal is cooled to room temperature with a speed from the range of 10-100 degrees / hour.

The resulting crystal is annealed in air, either in an inert gas atmosphere or in vacuum at a temperature in the range of 500-950 ° C for a time interval of not more than 100 hours.

Example 1

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd ₂ Y _0.968 Ce _0.03 Mg _0.002 Ga _2.9998 Al ₂ Be _0.0002 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 2

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd _1.5 Y _1.462 Ce _0.03 Mg _0.008 Ga _2.903 Al ₂ Be _0.097 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 3

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd ₁ Y _1.9688 Ce _0.03 Ca _0.0012 Ga _2.9998 Al ₂ Be _0.002 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, and calcium carbonate CaCO ₃ .

Example 4

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd ₂ Y _0.74 Ce _0.03 Ca _0.23 Ga _2.903 Al ₂ Be _0.097 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO and calcium carbonate CaCO ₃ .

Example 5

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition Gd _1.9695 Y ₁ Ce _0.03 Sr _0.0005 Ga _2.9998 Al ₂ Be _0.002 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, and strontium carbonate SrCO ₃ .

Example 6

To grow a single crystal according to the Czochralski method, the initial charge corresponding to the composition Gd _1.86 Y ₁ Ce _0.03 Sr _0.11 Ga _2.903 Al ₂ Be _0.097 O _{12 was used}

and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, and strontium carbonate SrCO ₃ .

Example 7

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition Gd _0.9697 Y ₂ Ce _0.03 Ba _0.0003 Ga _2.9998 Al ₂ Be _0.0002 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, and barium carbonate BaCO ₃ .

Example 8

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition Gd _1.902 Y ₁ Ce _0.03 Ba _0.068 Ga _2.903 Al ₂ Be _0.097 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, and barium carbonate BaCO ₃ .

Example 9

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd _1,9888 Y ₁ Ce _0,01 Mg _0,0012 Ga _2,9998 Al ₂ Be _0,0002 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 10

To grow a single crystal by the Czochralski method has been used initial charge, corresponding to composition Gd _1.968 Ce _0.03 Y ₁ Mg _3.9998 Al _0.002 Ga ₁ O ₁₂ Be _0.0002 and synthesized from a mixture of oxides of Gd ₂ O _3, Y ₂ O _3, Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 11

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd _1.5 Y _1.4682 Ce _0.03 Mg _0.0018 Ga _1.9998 Al ₃ Be _0.0002 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 12

To grow a single crystal by the Czochralski method, we used the initial charge corresponding to the composition Y _2.9685 Ce _0.03 Mg _0.0015 Ga _2.9998 Al ₂ Be _0.00015 O ₁₂ and synthesized from a mixture of oxides Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 13

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd _2.5681 Y _0.4 Ce _0.03 Mg _0.0019 Ga _2.9998 Al ₂ Be _0.0002 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 14

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition of Gd _2.836 Y _0.07 Ce _0.03 Mg _0.0064 Ga _2.9956 Al ₂ Be _0.0044 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 15

To grow a single crystal by the Czochralski method has been used initial charge, corresponding to composition Gd _1.922 Ce _0.03 Y ₁ Mg _2.9968 Al _0.048 Ga ₂ O ₁₂ Be _0.0032 and synthesized from a mixture of oxides of Gd ₂ O _3, Y ₂ O _3, Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 16

To grow a single crystal by the Czochralski method has been used initial charge, corresponding to composition Gd _1.952 Ce _0.01 Y ₁ Mg _2.5975 Al _0.038 Ga ₂ O ₁₂ Be _0.0025 and synthesized from a mixture of oxides of Gd ₂ O _3, Y ₂ O _3, Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO, MgO.

Example 17

To grow a single crystal by the Czochralski method, we used the initial mixture corresponding to the composition Gd _2.824 Y _0.1 Ce _0.03 Mg _0.046 Ga _2.9972 Al ₂ Be _0.0028 O ₁₂ and synthesized from a mixture of oxides Gd ₂ O ₃ , Y ₂ O ₃ , Ga ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , BeO ₂ , MgO.

From the grown single crystals, samples were made for measurements in the form of disks with a diameter of 25 mm and a thickness of 7 mm.

Scintillation yield measurements were carried out by the standard method for gamma spectroscopy. The samples were mounted on a PHILIPS XP2020 photomultiplier tube through optical immersion grease, covered with a reflector, and irradiated with a Cs-137 gamma source with an energy of 662 keV gamma rays. Amplitude spectra were accumulated in a multichannel amplitude analyzer. The scintillation yield of the samples relative to each other was determined as the ratio of the positions of the peaks of total absorption of 662 keV gamma rays on the scale of the amplitude analyzer.

The scintillation kinetics were measured using the delayed coincidence method. For measurements, we used a measuring stand based on a Na-22 annihilation gamma-ray source, a two-channel measuring setup with a “start” channel based on a CsF scintillation crystal and a PHILIPS XP2020 photomultiplier, and a stop channel based on a PHILIPS XP2020Q photomultiplier. Temporal reference to the signals of photoelectronic multipliers was carried out by two shapers with a tracking threshold, the signals from which were fed to a time-amplitude converter, which converts the difference in the arrival times of start and stop signals to an output voltage pulse with an amplitude proportional to this difference, which then goes to a multi-channel amplitude analyzer. The measured scintillation kinetics spectra were processed in the ROOT v.5.26 software package, the time constants of the main emission component and its weight (fraction) in the scintillation kinetics were determined.

Afterglow was measured by a method similar to that described in (K. Kamada, et al., Alkali earth co-doping effects on luminescence and scintillation properties of cadoped Gd3A12Ga3O12 scintillator, Opt. Mater. (Amst). 41 (2015) 63-66. doi: 10.1016 / j.optmat.2014.10.10.008). The measurements were carried out in the photon counting mode by measuring the counting speed from a PHILIPS XP2020 photomultiplier tube: a) 100 s after stopping the irradiation of the sample with an X-ray source for 15 minutes Sa, b) measuring the counting speed immediately before the irradiation of the Sb sample, and c) measurement " dark "count rate without a sample installed on the photomultiplier tube Sc. Samples were mounted on a photomultiplier tube through an optical diaphragm with a diameter of 1 mm in order to reduce the maximum count rate and to prevent the transmission of pulses when determining the count rate during irradiation of the sample. The count rate was measured using a digital frequency meter. The discrimination threshold of the frequency meter was set so low as to capture most of the samples at the single-electron peak of the photomultiplier tube, but at the same time avoid registration of low-amplitude electronic noise. The phosphorescence level was determined as the percentage ratio of the count rates (Sa - Sc) / (Sb - Sc).

The use of this invention allows to obtain a single crystal with a garnet structure for scintillation sensors, having in the temperature range from plus 25 ° C to plus 150 ° C, inclusive, the following characteristics:

Light output at a temperature of plus 25 ° C, not less than 51000 ph / MeV;

Light output at a temperature of plus 150 ° C, not less than 20,000 ph / MeV;

The duration of the main component of the kinetics of scintillation is not more than 55 ns;

The proportion of the main component of the kinetics of scintillation is at least 89%;

The phosphorescence level after 100 s,% - not more than 0.5%;

The advantages of this invention are provided by the fact that as a result of the joint activation of yttrium-gadolinium-aluminum-gallium garnet, described by the formula ((Gd _1-r Y _r ) _1-sx Me _s Ce _x ) _3-z (Ga _1-yq Al _y Be _q ) _{5 + z} O ₁₂ , ions of cerium, beryllium and one of the metals from the series Mg, Ca, Sr in a given concentration range, where q is in the range from 0.00001 to 0.02; r is in the range from 0.05 to 0.95; x is in the range from 0.001 to 0.01; y is in the range from 0.2 to 0.6; z is in the range from -0.2 to 0.2; s is in the range from 0.0001 to 0.1, while Me denotes at least one element from the series Mg, Ca, Sr, scintillation yield increases over a wide temperature range from plus 25 ° С to plus 150 ° С, inclusive, and, as a result, the energy resolution is improved when registering γ-quanta with energy in a wide temperature range, in particular γ-quanta with an energy of more than 500 keV. This allows expanding the possibilities of using scintillation material in areas where a high energy resolution is required in the temperature range up to plus 150 ° С, inclusive.

Claims (10)

1. Scintillation material with a garnet structure for scintillation sensors, which is a compound described by the chemical formula ((Gd _1-r Y _r ) _1-sx Me _s Ce _x ) _3-z (Ga _1-yq Al _y Be _q ) _{5+ z} O ₁₂ , and the q value is in the range from 0.00001 to 0.02; the value of r is in the range from 0.05 to 0.95; the value of x is in the range from 0.001 to 0.01; the value of y is in the range from 0.2 to 0.6; the value of z is in the range from -0.2 to 0.2; the value of s is in the range from 0.0001 to 0.1, while Me denotes at least one element from the series Mg, Ca, Sr. 2. The scintillation material according to claim 1, characterized in that when the gamma rays are irradiated with the aforementioned compound, the fluorescent component generates radiation at a wavelength in the range of 480-680 nm. 3. The scintillation material according to claim 1, characterized in that the light output at a temperature of 25 ° C is at least 51,000 ph / MeV. 4. The scintillation material according to claim 1, characterized in that the light output upon irradiation with a Cs-137 gamma source with 662 keV gamma-quanta energy at a temperature of plus 150 ° C is at least 20,000 ph / MeV. 5. The scintillation material according to claim 1, characterized in that the light output upon irradiation with a Cs-137 gamma source with 662 keV gamma-quanta energy at a temperature in the range of 25-150 ° C changes at a rate of not more than -0.4% / deg. 6. The scintillation material according to claim 1, characterized in that the duration of the main component of the kinetics of scintillation is not more than 55 ns. 7. The scintillation material according to claim 1, characterized in that the proportion of the main component of the kinetics of scintillation is at least 85%, and the phosphorescence level after 100 s is at most 0.5%. 8. A method for producing a scintillation material with a garnet structure for scintillation sensors according to claim 1, including the preliminary preparation of a mixture of stoichiometric composition in accordance with the chemical formula of the compound according to claim 1 from a mixture of oxides Gd, Y, Ga, Al, Mg, Be, the introduction of cerium in the form of a compound taken from a series of oxide, or fluoride, or chloride, as well as Ba, or Sr, or Ca in the form of carbonate, and the subsequent growth of single crystals from the resulting mixture according to the Czochralski method. 9. The method according to p. 8, characterized in that the growth of single crystals by the Czochralski method is carried out in a protective atmosphere based on argon or nitrogen with the addition of oxygen in a concentration from the range from 0, 0001 to 5 vol.%, 10. The method according to p. 8 characterized in that the grown single crystal is subjected to isothermal annealing at a temperature from the range of 500-950 ° C for a time from the range of not more than 100 hours, either in air or in an inert gas atmosphere or in vacuum.